<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* .demo span{
            width: 200px;
            height: 200px;
            background-color: aqua;
        } */
         div{

         }
    </style>
</head>
<body>
    <!-- <div class="demo">
        
        <span>child1</span>
        <span>child2</span>
        <span>child3</span>
    </div> -->
    <div>
        hello
    </div>
</body>
</html>